Air conditioners and heat pumps commonly employ vapor-compression refrigerant systems to cool, or both cool and heat air supplied to a climate controlled comfort zone within, for example, a residence, office building, hospital, school, restaurant or other facility. Conventionally, such vapor-compression systems include a compressor, condenser, an expansion device, and an evaporator connected to one another by refrigerant lines in a closed refrigerant circuit and arranged according to the vapor-compression cycle employed (i.e. heating or cooling). The condenser and the evaporator include a heat exchanger that generally acts to add heat to or remove heat from refrigerant flowing through the devices.
Heat exchangers employed in condensers and evaporators commonly include a number of coils through which the refrigerant flows, fins connecting adjacent coils to one another, and manifolds for delivering the refrigerant to the coils. The coils may be stacked vertically or horizontally in generally parallel relationship to one another and be connected between an input manifold and an output manifold. The manifolds, sometimes referred to as headers, may be, for example, closed ended tubes configured as inlet and outlet paths for refrigerant flowing to and from the coils. Pairs of adjacent coils are connected by a number of fins distributed longitudinally between the coils. The fins structurally join the coils, as well as direct air across the coils and facilitate heat transfer between the coils and the air passing over the coils. The fins are commonly constructed from a thin piece of thermally conductive material stamped into the desired shape and cut to fit the coils of the particular heat exchanger. For example, the fins may be formed from a thin piece of sheet metal that is stamped to form a number of corrugations across the length of the sheet. The corrugated sheet may then be cut into strips, each of which may form the fins joining two adjacent heat exchanger coils.
In order to stamp the sheet metal stock into the desired fin shape, the metal must be lubricated. Prior techniques commonly lubricated the fin stock by feeding the stock through an oil bath and one or more rollers in an attempt to spread the oil evenly across the stock with a desired thickness. Such techniques are directed at removing excess oil from the stock instead of applying the correct amount of oil distributed over the stock at the correct thickness. Oil bath techniques have proven unreliable at lubricant film thicknesses less than approximately 0.0254 mm (0.001 inches). Additionally, these techniques inherently produce a significant amount of waste, as well as provide little to no control over the application process.